Bach’s St Matthew Passion is sometimes seen as the opera he never wrote. It is sprawling, musically ambitious and acutely dramatic, boasting a large cast as well as two choirs and orchestras. This performance from the Armonico Consort and Baroque Orchestra – directed from the harpsichord by Christopher Monks and with Ian Bostridge as a guest-star Evangelist – did much to highlight the piece’s equivocations between the sacred and the secular.

For a start, there were the tempi. Monks took much of the Passion at a considerable lick, digging down to the dance forms beneath the musical surface. Then there was the sound. At its best, the orchestra generated a muted period-instrument warmth, with solo lines sometimes boldly, expressively sensuous. Under the hall’s ferocious spotlights, however, tuning gradually became a challenge, and that sensuousness became increasingly effortful.

More explicitly devotional, the voices of the Armonico Consort were beautifully blended, with crisp diction and slow-release suspensions as standard. Their chorales were pure pleasure, the final appearance of the repeated Passion harmonisation exquisitely tranquil. But as a roster of bit-part soloists, they were uneven and often overstretched. Best of the bunch was countertenor Joseph Bolger, whose Erbarme dich was compelling, its long lines gorgeously sculpted.

And then there was Bostridge. Offset by Andrew Davies’s light, lyrical Christus, Bostridge grimaced, keened and snarled his way through the evening – an operatic Evangelist par excellence. It wasn’t always polished; it wasn’t always subtle. But his energy and unwavering commitment galvanised this mixed performance.